The sequence of three nucleotides that code for specific amino acids or stop signals in the synthesis of protein is called an?

Codon. The genetic code comprises of all the codons in the genome. Codons, other than the stop codons, code for 20 amino acids. Codons, that are comprises of three nucleotides, have a possible 64 combination from permutation computation.  61 of these combiantions code for proteins while the rest stop translation.  

trachea, alveoli, lung capillaries, arteries